Human hepatocytes will be derived from cadaver organ donors or from discarded surgical material by a modified collagenase perfusion technique and will be stored in liquid nitrogen according to defined protocols. Cell cultures of human hepatocytes and transplanted human nepatocytes will be used to study the effects of chemical carcinogens. Suspensions of human hepatocytes will be used to study the metabolism of specific chemical carcinogens, the amount of carcinogen-DNA adducts that they generate and the unscheduled DNA synthesis that these adduts elicit. Combined cultures of human hepatocytes on human fibroblasts will be used to study mutagenesis of human fibroblasts induced by procarcinogens and mediated by hepatocytes. The relative distribution of DNA-carcinogen adduts on the two cell types will also be determined in combined cultures. Human hepatocytes will be transplanted into nude mice. The system will be characterized morphologically, histochemically and in terms of cell kinetics. The reproductive survival of human hepatocytes after exposure to chemical carcinogens will be quantitated by constructing survival curves with the transplantation technique. The neoplastic transformation of human hepatocytes will also be assessed by adapting already available initiation-promotion protocols for rat hepatocarcinogenesis to the human hepatocyte transplantation system. Studies in all these areas using rat hepatocytes are already underway in our laboratories and the data from rat hepatocytes will provide the reference for interspecies comparisons.